Depositional environment and morphometric analysis of pebbles from a river bed at Odufor, Etche in Rivers State, Nigeria

In this study, the depositional environment of parts of Etche in Rivers State was determined using pebble morphometric analysis. This involved the collection and classification of approximately 100 pebble samples from stream deposits at Odufor, Etche. Morphometric measurements taken, included the Long (L), Intermediate (I), and Short (S) axes, using a Vernier caliper. These raw data were then used to calculate indices such as Flatness Ratio (FR), Elongation Ratio (ER), Maximum Sphericity Projection Index (MPSI), and Oblate–Prolate (OP) Index. Results from the analysis showed that the flatness ratio had an average value of 0.52 ± 0.12, elongation ratio (ER) has values within the range of 0.98– 0.65 with mean value of 0.84 ± 0.08, The roundness has values ranging from 10% to 90% with mean value of 45.5% all suggesting a fluvial environment. While the mean maximum projection sphericity index (M.P.S.I) for pebbles is 0. 36± 0.04 with range of 0.48 to 0.94 indicates a marine influence, But the Bivariate plot for flatness index vs sphericity (MPSI) showed that the pebbles beds from Odufor clustered in the fluvial area. The morphometric analysis of the pebbles suggests the presence of a mixed nature of transport and an environment of deposition that is presumably of fluvial with marine influence. This quantitative evaluation helps to verify the transport processes and interpret the depositional environments within the Niger Delta Basin.